Okay All, here is a big tool that is extremely useful when looking for anything from your next trainer to your next horse. I wish this was a more widely accessible tool, but whether you use USEF or USDF you need to have some variety of membership with the organization in order to use them. In past years there was Centerline Scores and Dressage Detective, but both are outdated and not available anymore. 
I find this to be especially useful when looking up clinicians and coaches- I always want to find a coach that has done what I want to do. So, in my case, I look up a coach and want to see their scores to GP and if they developed the horse through the levels. Obviously, there are other factors, but this is an easy place to start. Additionally, I think it is very useful to look up a potential horses (to purchase) scores to get a better idea of where they are at in their training. USEF is also a great tool for that as you can also see show records outside of dressage if they have competed in other disciplines. 
Here are little screen recorded tutorials on how to find these things: